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DY: Fachverband Dynamik und Statistische Physik

DY 24: Granular matter II

DY 24.4: Vortrag

Donnerstag, 28. Februar 2008, 10:45–11:00, MA 004

Granular convection, stripe pattern segregation and collective dynamics observed in a single experimental setup — •Frank Rietz and Ralf Stannarius — Otto-von-Guericke-Universität Magdeburg, Abteilung für Nichtlineare Phänomene

Pattern formation in continuously driven granulates has been studied extensively in recent years, but the observed phenomena are far from being well understood. In loosely packed (fluidized) granulates, dynamics of axially segregated stripes have been investigated in horizontally rotating mixers. Convection rolls have been found in vibrated containers. The fluid-like mobility of individual granular particles is restricted at dense pack, one observes a collective motion (dynamic glass transition) instead.

All these phenomena are found in combination in a single experiment, which is introduced here [1]. A flat container (Hele-Shaw cell) is filled with a granular mixture and afterwards rotated continuously about its horizontal long axis. The filling fraction is crucial for the observed effects. At partial filling, a pattern of axially segregated stripes appears, which undergoes slow coarsening. Periodically travelling stripes are observed, too. In an almost densely packed container regular convection rolls appear instead. The densely packed granulate moves in collective clusters and a serpent like segregation pattern appears.

[1] F. Rietz & R. Stannarius: On the brink of jamming: Granular convection in densely filled containers; Phys. Rev. Lett.; submitted